The present invention relates to a linear working unit which is used in such apparatuses as a robot or a measuring instrument.
As regards a linear working unit which is constructed, for use as a working arm of a simple robot or in a measuring instrument or the like, in such a manner that a nut block, being guided by a guide rail, is moved in the axial direction along with the revolving motion of a screw shaft driven with a motor, such a linear working unit which is disclosed, for example, in the Unexamined Japanese Utility Model Publication No. 193,637/1988 is generally known.
It is required of a measuring instrument or the like that two movable members move leftward and rightward in relation to a reference line, but no such unit has hitherto been known among the conventional linear working units. If it is to be attempted to realize such an operation with the conventional linear working units, it is necessary to provide two such units in series in such a manner that a movable member in one of these units is moved in one axial direction while the movable member in the other unit is moved in the opposite direction each working in correspondence to the other in a predetermined relative relation to the movable member in the former unit. Yet, such an arrangement of the two conventional linear working units would present the problem that it would be difficult to attain any sufficient accuracy in the movement of the two movable members in the linear direction or to attain any sufficient synchronization of their leftward and rightward movements. Also, such an arrangement of the two conventional linear working units would present the additional problem that it would be difficult to secure any proper relation of the relative positions of the two movable members.
Further, such an arrangement of the two conventional linear working units would present the still additional problem that it would be difficult to maintain any accurate parallelism of the two moving members in the direction of their linear movement or to maintain their well-regulated positions, so that the two movable members would generate vibrations and noises when they are set into high-speed operation and that these movable members fail to attain any satisfactory stability when they are brought to a stop, and, above all, those units with a long stroke are liable to cause vibrations.
Furthermore, such linear working units would be liable to wastefulness in manufacturing processes because it would be necessary, for instance, to change the positions of mounting holes for the installation of a guide rail in case the two movable members are to be adjusted to a variety of positions as the user requires in relation to the guide rails. In addition, the use of such two units would present the problem that it necessarily makes it impossible to assemble the two units in any light-weight and compact construction, with the inevitable result that the assembled product would be formed of a larger number of items of component parts and would be expensive.